Selective recovery of protonated dyes from dye wastewater by pH-responsive BCN material

Abstract In this work, it has firstly found that carbon-doped boron nitride (BCN) material has high affinity for proton and can be used as pH-responsive material to selectively recover protonated dyes neutral red (NR) and malachite green (MG) from dye wastewater. The maximum adsorption capacities of BCN for NR and MG are 747.10 mg·g−1 and 682.46 mg·g−1 which is obviously larger than that of methyl orange (MO 61.27 mg·g−1) and methylene blue (MB 119.38 mg·g−1). The adsorbed protonated dyes are easily released through pH changeing and the maximum recovery amounts of NR and MG are 704.94 mg·g−1 and 631.54 mg·g−1, respectively. The effects of inorganic ions (Cl−, SO42− and NO3−) and cationic surfactant on the adsorption performance of BCN to NR and MG can be negligible. By the adding of anionic surfactant, the adsorption and release performance of BCN to NR and MG is a little decrease. BCN can still selectively recover NR (or MG) from the mixed dye solutions. In two mixed dye solutions, the maximum recovery of BCN for NR (or MG) is above 90.93%. In ternary system, the maximum recovery of BCN for protonated dye is above 79.21%. In NR-MG-MB-MO quaternary system, the recovery of BCN for NR and MG is above 87.57%. Therefore, BCN has a good potential that is used to selectively recover the protonated dyes from dye wastewater.